Patterns of blood pressure and heart rate responses to the head-up tilt test
- III. interná klinika, Lekárska fakulta L. Pasteura, Univerzita P. J. Šafárika Košice, Slovenská republika.
Background:
The head-up tilt test represents a useful tool in detecting predisposition to vasovagally mediated syncope, but relations among physiological variables during the test and prediction of results in the earlier phase of tilting are not sufficiently elucidated.
Methods:
We evaluated the patterns of heart rate and blood pressure changes and their interrelationship during a 70-degree tilt depending on the type of predominant response in 125 patients with unexplained syncope. The baseline test lasted for 44 minutes. When tilting was negative, another 16 minutes were added after nitroglycerin provocation. According to their tilt response, patients were divided into four groups: (I) baseline cardioinhibiting, (II) baseline vasodepressor, group (III) had a syncope after the pharmacological provocation with nitroglycerin, group (IV) was head-up tilt test negative.
Results:
Time to syncope in the baseline positive groups was 31.2 ± 11.4 minutes, and 5.8 ± 3.4 minutes after nitroglycerin provocation. Polynomial regression showed characteristic patterns of blood pressure and heart rate progression in the respective groups, but did not allow predicting the outcome of the test. Patients developing syncope during the tilt test showed a parallel decrease in heart rate and blood pressure suggesting simultaneous worsening of the cardiomotor and the vasomotor branches of the baroreceptor reflex.
Conclusion:
Heart rate and blood pressure changes during the head-up tilt test were described by polynomial regression. Mathematical functions showed a relatively small predictive power relative to the likelihood of syncope occurrence during the tilt. Shortening of the tilt test may prevent occurrence of syncope.
Keywords: Neurocardiogenic syncope; Head-up tilt test; Blood pressure; Heart rate; Mathematical model
Published: May 1, 2005 Show citation